Reflector with a resistant surface

ABSTRACT

A reflector, with high total reflection, resisting mechanical stress, and having a reflector body on which the following components are superimposed (a) a functional coating, e.g., a varnish, (b) a reflection layer structure composed of a reflecting metallic layer and, optionally, one or more transparent ceramic layers, having for instance an optical depth of λ/2, applied on the top of the metallic layer. The reflection layer structure is a protection layer as a surface layer. The protection layer is a silicon oxide of general formula SiO x  where x is a number from 1.1 to 2.0, or is an aluminum oxide of formula Al 2 O 3 , with a thickness of 3nm or more. The protection layer protects the underlying layers from mechanical stresses. In the DIN 58196 wipe test, the protected layer shows no damage after 50 test cycles, each with 100 wiping strokes. These reflectors are useful in the field of lighting and illumination where they can be used for lighting of display units with screens, primary lighting, secondary lighting, raster lighting, light ceilings or light deflector lamella.

This is a 371 of PCT/CH98/00487, filed on Nov. 12, 1998, that hasbenefit of European Patent Application 97810881.9, filed on Nov. 19,1997.

BACKGROUND OF THE INVENTION

The invention relates to a reflector with high total reflection,resisting mechanical stress and comprising a reflector body of metal andarranged thereon superimposed,

BACKGROUND ART

a) a functional coating, made of a gel-film, lacquer or polymer ofthickness 0.5 to 20 μm or, in the case of a reflector body of aluminium,also of anodically oxidised aluminium formed directly out of thealuminium lying on the surface of the reflector body, of thickness 10 to1500 nm, and

b) a reflection layer structure composed of a reflecting layer and aplurality of transparent layers.

The invention also concerns the use of such reflectors.

It is generally known to produce strips of highly reflective materialssuch as e.g. high purity aluminium or AlMg alloys based on aluminiumwith a purity level of 99% and higher, such as e.g. 99.5%, and toproduce roll surfaces that create diffuse or directional reflection,depend-ing on the application. It is also known, in order to increasethe directional reflection (degree of reflection), to brighten thesurfaces of such strips chemically or electrolytically and sub-sequentlyto provide them with a protective, e.g. 1.5 μm thick layer by anodicoxidation.

The known processes have the further disadvantage that high purity andexpensive alloys based on high purity aluminium have to be employed. Theanodic oxide layer causes the degree of reflection to be lowered and, asa result, both the total reflection and the directional reflection, dueto absorption and diffuse light scattering, in particular in the oxidelayer. This represents a loss of energy.

Known from EP-A-0 495 755 are items with surfaces of aluminium which aresuitable for depositing layer systems from the gas phase onto thesesurfaces. Anodising the surface is dispensed with and a layer system isdescribed comprising e.g. an adhesive layer, such as a ceramic layer, alight reflecting layer, such as a metallic layer e.g. of aluminium andone or more transparent protective layers e.g. of the oxides, nitridesor fluorides of magnesium, titanium or praseodymium. Such layer systemsexhibit a high degree of reflection. Such a layer system, however, hasthe disadvantage of being very sensitive to mechanical effects.

BROAD DESCRIPTION OF THE INVENTION

EP-A-0 586 943 describes the precipitation of a reflection layer whichis based on aluminium and superimposed on this a gel film that has beendeposited on the aluminium by a sol-gel process. The reflection isachieved by a layer system comprising layers of silicon oxide, metal,silicon dioxide and titanium dioxide. This is also a possibility forachieving reflecting aluminium-based materials. The layer structuredescribed in EP-A 0 568 943 is not resistant to mechanical stress to thedesired degree.

The document WO 97/01775 describes bent reflectors with a reflector bodyof glass and provided thereon a primary layer of silicon or silicon andstainless steel and, situated on top of that, a reflecting metal layerwhich is covered by a protective layer e.g. of silicon-nitrite.

Known from EP-A-O 456 488 are reflectors having a foundation and areflecting layer provided thereon and a subsequent layer systemcomprising high and low refractive index layers, where the reflectinglayer is deposited directly on the substrate or on a dielectric layer.The layer system may be covered by a protective layer.

The object of the present invention is to avoid the above mentioneddisadvantages and to propose reflectors with outer layers that areinsensitive to external mechanical stress and are characterised by ahigh resistance to wiping.

That objective is achieved by way of the invention in that thereflection layer structure comprises a silicon oxide of general formulaSiO_(x) where x represents a number from 1.1. to 2.0, or aluminium oxidehaving the formula Al₂O₃, of thickness 3 nm (nanometre) or more asprotective layer and the protective layer as the layer lying on thesurface protects the under-lying layers against mechanical damage andthe protective layer exhibits no surface damage in the wipe testaccording to DIN 58196 after 50 test cycles each of 100 wiping strokes.

DETAILED DESCRIPTION OF THE INVENTION

In the present invention the protective layer basically belongs to thetransparent layers within the structure of reflection layers.

In one useful version the minimum thickness of the protective layeramounts to 3 nm. The maximum thickness of the protective layer may e.g.be 1000 nm, advantageously 400 nm. In another version the thickness ofthe protective layer is preferably 40 nm or less. In particular thethickness of the protective layer is 3 to 20 nm. In the presentdescription of the invention the letters nm stand for nanometre.

In a further version the thickness of the protective layer can also bedefined by its optical thickness (or depth). The optical thickness ispreferably described by the formula n·d=λ/2±40 nm. The optical thicknessmay also be a multiple thereof expressed by k, where k is a naturalnumber such as 2, 3, 4, 5, 6. 7, 8, 9 or 10. In this formula n standsfor the index of refraction and d the geometric thickness. The symbol λstands for the intensity maximum of the wave lengths of the reflectedelectromagnetic radiation. In the case of visible light λ lies in theregion of approximately 550 nm.

The reflecting body in question may be any three-dimensional objecthaving at least one free surface of a metal, such as iron, steel,aluminium or aluminium alloy. These free surfaces may be an aluminiumwith a purity of 98.3% and higher in certain cases with a purity of forexample 99.0% and higher, 99.7% and higher, 99.9% and higher or 99.95%and higher. Apart from aluminium of the above mentioned purities thesurface may also be of an alloy. Preferred alloys are those belonging tothe AA 1000, AA 3000 and AA 5000 series. Further preferred alloyscontain e.g. 0.25 to 5 wt. % magnesium, in particular 0.5 to 4 wt. %magnesium, or 0.2 to 2 wt. % manganese, or 0.5 to 5 wt. % magnesium and0.2 to 2 wt. % manganese, in particular e.g. 1 wt. % magnesium and 0.5wt. % manganese, or contain 0.1 to 12 wt. % copper, preferably 0.1 to 5wt. % copper, or contain 0.5 to 6 wt. % zinc and 0.5 to 5 wt. %magnesium, or contain 0.5 to 6 wt. % zinc, 0.5 to 5 wt. % magnesium and0.5 to 5 wt,% copper, or contain 0.5 to 2 wt. % iron and 0.2 to 2 wt. %manganese, in particular e.g. 1.5 wt. % iron and 0.4 wt. % manganese orAlMgSi alloys or AlFeSi alloys. Further examples are AlMgCu alloys suchas A199.85Mg0.8Cu or AlMg alloys such as AlMg1.

Especially preferred free surfaces are e.g. of aluminium having a purityof 99.5 % and higher, 99.8% and higher, 99.85% and higher or surfaces ofan aluminium alloy containing 0.5 wt. % magnesium or containing 1 wt. %magnesium, or containing aluminium having a purity of 99% and 5 to 10 wt% magnesium, in particular 7 wt. % magnesium and 6 to 12 wt. % copper,in particular 8 wt. % copper. Especially preferred are also allaluminium alloys that can be rolled.

Examples of reflector bodies are castings and forgings and, inparticular, rolled products such as foils, strips, plates, sheets thatmay be shape-formed by bending, deep-drawing, cold impact extrusion andthe like. Further, extrusions, beams or other shapes may be employed.

Depending on the application in question, the whole reflector body maybe made of metal, preferably of the above mentioned aluminium oraluminium alloy; it is possible for only parts or only parts of thesurface area to be of metal.

The above mentioned metal and in particular the aluminium or aluminiumalloy may also be part or a part of a surface of a composite e.g. alaminated foil or laminates of any material of choice such as e.g.plastics or and metals such as Al-coated steel sheet or Al-coatedplastic.

The aluminium surfaces may also be subjected to a chemical orelectrochemical process or an alkaline pickling process. Suchbrightening or pickling processes are employed prior to anodising.

The aluminium surfaces may, for any topography of choice, exhibit asurface roughness R_(a) of e.g. 0.01 to 5 μm, preferably from 0.01 to0.5 μm. Further preferred, advantageous R_(a) roughness values are from0.01 to 0.4 μm and in particular from 0.03 to 0.06 μm, whereby 0.04 μmis especially suitable. The surface roughness characteristic R_(a) isdefined in at least one of the DIN standards 4761 to 4768.

In the case of the present reflectors at least one pre-treatment layermay be provided between the reflector body and the functional coatinga).

In the case of a reflector body made mainly out of ferrous based metal,the pre-treatment layer may be a layer made by phosphate or chromatetreatment or by zinc plating. In the case of a reflector body made ofaluminium the pre-treatment layer may be a layer formed by chromate orphosphate treatment or by anodising. The pre-treatment layer ispreferably made of anodised aluminium and is created directly out of thealuminium on the surface of the reflector body. The pre-treatment layermay have a thickness e.g. of at least 10 nm, usefully 20 nm,particularly useful is a thickness of at least 50nm, preferably at least100 nm and especially preferably at least 150 nm. The greatest thicknessof the pre-treatment layer may e.g. be 1500 nm, preferably 200 nm. Thepre-treatment layer has therefore a thickness of preferably 100 nm to200 nm.

For example the pre-treatment layer may be an anodic oxide layer formedin a redisolving or non-redisolving layer electrolyte. The pre-treatmentlayer may also be a yellow chromate layer, a green chromate layer, aphosphate layer or a chrome-free pre-treatment layer which is formed inan electrolyte containing at least one of the elements Ti, Zr, F, Mo orMn.

The functional coating a) is deposited directly onto the reflector bodyor—if present—on the pre-treatment layer. In the case of an anodic oxidelayer the aluminium oxide layer formed by anodising may form thefunctional coating.

For example, the functional coating a) exhibits a thickness of 0.5 to 20μm, usefully 1 to 20 μm, preferably 2 to 10 μm and especially preferably2 to 5 μm. If the aluminium oxide layer formed by anodising forms thefunctional coating a), then its thickness, as mentioned above, is from20 to 1500 nm.

The functional coating a) may e.g. be a gel film deposited using asol-gel process. Further functional coatings a) are lacquers orpolymers, thereby advantageously vacuum resistant lacquers and polymers,polyesters, epoxy, polycarbonates, acrylic, polyvinylchloride,poly-vinyl-fluoride, polyvinylidenfluoride etc.

The gel film may be a coating with organo-functional silanes of a metalcompound and may e.g.

A) have been obtained by hydraulic condensation of the followingcomponents, if desired in the presence of a condensation catalyst and/orthe normal additives:

1. at least with one cross-linkable organo-functional silane of acompound having the formula (II):

R′″_(m)SiX_((4−m))  (II)

 in which the groups X, which may be the same or different, representhydrogen, halogen, alk-oxy, acyloxy, alkylcarbonyl or —NR″2(R″=H and/oralkyl) and the radicals R′″, which may be the same or different,represent alkyl, alkenyl, alkinyl, aryl, arylalkyl, alkylaryl,arylalkenyl, alkenaryl, arylalkinyl or alkinylaryl, where these radicalsmay be interrupted by O or S atoms or by the group —NR″ and one or moresubstituents from the group of halogens and may, if desired, bear thesubstituted amino, amide, aldehyde, keto, alkylcarbonyl, carboxy,mercapto, cyano, hydroxy, alkoxy, alkoxycarbonyl, sulphonic acid,phosphoric acid, acryloxy, methacryloxy, epoxy or vinyl groups, and mhas the value 1, 2 or 3, and /or with an oligomer derived therefrom,whereby the radical R′″ and/or the substituent must be a cross-linkableradical or substituent, of an amount equal to 10 to 95 mol. %, withreference to the total mol number of the (monomer) starting components;

2. at least of one metal compound having the general formula III:

MeRy  (III)

 In which Me is a metal from the group comprising Al, Zr, Ti, where y inthe case of aluminium is 3 and in the case of Ti and Zr is 4 and theradicals R, which may be the same or different stand for halogen, alkyl,alkoxy, acyloxy or hydroxy, where the just mentioned groups may bepartially or wholly replaced by chelate ligands and/or with an oligomerand/or, if desired, a complex aluminium salt of an inorganic or organicacid, in an amount of 5 to 75 mol %, with reference to the total molnumber of the (monomer) starting components,

3. if desired, at least with one non-cross-linkable organo-functionalsilane having the formula I:

R′_(m)SiX_((4−m))  (I)

 in which the groups X, which may be the same or different, stand forhydrogen, halogen, hydroxy, alkoxy, acyloxy, alkylcarbonyl or —NR″2(R″=Hand/or alkyl) and the radicals; R′, which may be the same or different,represent alkyl, aryl, arylalkyl or alkylaryl, whereby these radicalsmay be interrupted by O or S atoms or by the group —NR′, and one or moresubtituents from the group of halogens and may, if desired, bear thesubstituted amide, aldehyde, keto, alkylcarbonyl, carboxy, cyano,alkoxy, alkoxycarbonyl groups, and m has the value 1, 2 or 3, and /orwith an oligomer derived therefrom, in an amount equal to 0 to 60 mol.%, with reference to the total mol number of the (monomer) startingcomponents;

4. if desired, with one or more low-volatile oxides of an element of anelement of the main group Ia to Va or the sub-groups IIb, IIIb, Vb toVIIIb of the periodic system with the exception of aluminium, whichis/are soluble in the reaction medium, and /or one or more compounds ofone of these elements which, under the reaction conditions, forms a lowvolatile oxide, in an amount of 0 to 70 mol %, with reference to thetotal mol number of the (monomer) starting components; and

B) such that an organic pre-polymer is added to this hydrolyticcondensate, whereby the reacting cross-linkable groups of the radicalR′″ and/or the cross-linkable substituents on the radical R′″ can becross-linked with those on the pre-polymer, or to advantage are of thesame name, and the pre-polymer is added in an amount of 2 to 70 mol %,with reference to the total mol number of the (monomer) startingcomponents;

C) the coating solution thus obtained is deposited onto a substrate, inparticular onto the reflector body or the pre-treatment layer thereon,and subsequently hardened.

Further details and information concerning the functional coatings a) inthe form of a gel-film may be found in EP-A 0 610 831 and EP-A 0 358011.

The above mentioned silanes may be replaced by compounds which containtitanium, zirconium or aluminium instead of silicon. This way thehardness, density and refractive index of the functional coating may bevaried. The hardness of the functional coating may also be controlled byuse of different silanes, e.g. by forming an inorganic network tocontrol the hardness and thermal stability, or by use of an organicnetwork to control the elasticity. A functional coating, which may beprovided between the inorganic and organic polymers, is deposited on thealuminium substrates e.g. via a sol-gel process by specific hydrolysisand condensation of alkoxides, principally those of silicon, aluminium,titanium and zirconium. In the process an inorganic network is createdand, via appropriate derivated silicate esters, additional organicgroups can be incorporated therein which on the one hand are employedfor functional purposes and, on the other hand, are used to createdefined organic polymer systems. Furthermore, the gel film may also bedeposited by electro-immersion using the principle of catephoricdeposition of an amine and organically modified ceramic.

The functional coating a), as the above mentioned silanes or the abovementioned lacquers, may be deposited by immersion, brush application,roll deposition, centrifugal application, spraying, so called coilcoating etc. onto the reflector body directly or over a pre-treatmentlayer.

After coating the anodised surface of the reflector body with thefunctional coating a), the coating can be hardened. The hardening maytake place by radiation such as UV-radiation, electron beam radiation orlaser beam radiation and/or at elevated temperature. The temperature mayraised by convection or thermal radiation such as infra-red and/orultra-violet radiation, or by a combination of convection and thermalradiation such as UV and/or IR radiation or using hot gas such as hotair. The temperature, measured at the layer below the functional coatinge.g. the metal layer such as the aluminium layer is greater than 110°C., usefully greater than 150° C. and preferably between 150 ° C. and240° C. For clear lacquers these temperatures are e.g. often 230° C. to240° C. The elevated temperature may e.g. be applied to the reflectorbody for 10 to 120 min. The convection heating may usefully be performedby applying heated gases, such as air, nitrogen or mixtures thereof.

The functional coating a) effects a levelling or smoothing of thesurface. R_(a) values for example of less than 0.01 μm and preferablyless than 0.02 μm are achieved. The surface roughness R_(a) is definedin at least one of the DIN standards 4761 to 4768.

The functional coating a) may be a single layer i.e. a monolayer or amultiple layer, such as e.g. a double layer, triple layer etc. Themultiple layers such as the double layers or triple layers may all be ofthe same material or of different materials, each selected from theabove mentioned materials for functional coatings a). The double layercoating, triple layer coating etc. may be formed e.g. by depositingfirst one layer, pre-hardening or hardening the first layer, depositingthe second layer and hardening the second layer. A first layer which hasonly been pre-hardened may be hardened along with the second layer.Should a third layer be deposited, then the first and the second layersmay be hardened or pre-hardened, and the hardening may concern only thethird layer or the hardening of the underlying layers—provided this isstill necessary—may be performed along with the hardening of the thirdlayer. Analogously, the same applies for further layers e.g. a fourthlayer etc. Preheating includes processes such as allowing to dry,pre-drying under the influence of heat or radiation, or the applicationof radiation or heat treatment. The useful thickness of a double ortriple layer lies in the above mentioned range of 1 to 20 μm, wherebyeach individually deposited layer may have a thickness e.g. of 2 to 5μm.

The reflecting layer structure b) contains a reflecting layer such ase.g. a layer of aluminium, silver, gold, chromium, nickel or alloys,e.g. containing mainly at least one of these metals. The thickness ofthe reflecting layer may e.g. amount to 10 to 200 nm (nanometre). As arule the reflecting layer is applied directly onto the functionalcoating a) or onto an inter-mediate bonding layer.

Further, the reflecting layer structure b) contains a plurality oftransparent layers. The transparent layers are deposited onto thereflecting layer. For example 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10transparent layers—not including the protective layer—advantageouslysatisfy the formula λ/2 with respect to the optical thickness for eachlayer, whereby in particular each of these transparent layers is adouble layer made up of two layers of thickness λ/4. The opticalthickness of each transparent layer having the formula λ/2 may vary by±40 nm. Preferred is one transparent layer or, also preferred are two,three or more transparent layers, which may be of the same or differentmaterials, where each of the transparent layers has an optical thicknessof λ/2±40 nm, and in particular, a double layer of thickness 2·λ/4. Theprotective layer, which is also transparent, is deposited on the abovementioned transparent layer or layers as the uppermost layer or as thelayer on the surface. λ corresponds to the intensity maximum of thewavelength of reflecting electromagnetic radiation.

The material of the transparent layers is of or contains e.g. oxides,nitrides, fluorides, sulphides etc. of alkali metals e.g. Li, Na, K,alkali-earth metals e.g. Mg, Ca, Sr, Ba, semi-metals such as Si,transition metals e.g. Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Y, Zr, Nb, Te, Ru,Pd, Hf, Ta, W, Re, Os, Ir, Pt, lanthanides e.g. La, Ce, Pr, Nd, Pm, Dy,Yb, Lu etc. One may mention here by name SiO_(x) where x stands for 1.1to 2.0, preferably 1.8, Al₂O₃, MgF₂, TiO₂, B₂O₃, Be-oxide, ZnO, SnO₂,Indium-tin-oxide (ITO), CdS, CdTe and hafnium- and zirconium-oxides.Advantageously, at least one of the transparent layers, with theexception of the protective layer, exhibit other materials than theprotective layer itself. One, several or all transparent layers ofoptical thickness λ/2±40 nm may be double layers each of two layers ofoptical thickness of λ/4. The double layers, each of two layers ofoptical thickness λ/4 are to advantage of a low refractive index layerof optical thickness λ/4 and a high refractive index of opticalthickness λ/4. The double layers are—especially to advantage—made up oftwo layers namely a first and a second layer of optical thickness λ/4i.e. a low refractive index first layer of optical thickness λ/4 of SiO₂or MgF₂ and a high refractive index second layer of optical thicknessλ/4 of Ti-oxide or Ti,Pr-oxide.

Accordingly, in order to reinforce the degree of refraction as a resultof parallel reflection at the phase boundary, one, two or moretransparent layers of optical thickness λ/2 may be formed out of twotransparent layers of optical thickness λ/4 using materials withdifferent refractive indices. The individual transparent layers with anoptical thickness λ/4 are typically from 30 nm, preferably from 40 nm,to 200 nm thick. One example of a transparent layer with an opticalthickness of λ/2 made up of two layers of optical thickness λ/4 maycontain a low refractive index layer of optical thickness λ/4 made ofSiO₂, MgF₂ etc. and a high refractive index layer of optical thicknessλ/4 of Ti-oxide, Ti,Pr-oxide, tantalum oxide etc.

Preferred are also reflection layer structures b) made up of areflecting layer, on top of that one or two transparent layers, each ofthese transparent layers in the form of double layers λ/4 and thereforeof optical thickness λ/2, and a protective layer which lies on thesurface of the transparent layers, and out of a silicon oxide having thegeneral formula SiO_(x), where x stands for a number between 1.1 to 2,or out of aluminium oxide, whereby the thickness of the protective layeris 3 nm or greater.

Preferred are also reflection layer structures comprising a reflectinglayer, on top of this a transparent layer of optical thickness λ/4 oflow refractive index and on top of this a transparent layer of opticalthickness λ/4 of high refractive index and a protective layer which lieson the surface made of a silicon oxide having the general formulaSiO_(x), where x stands for a number of 1.1 to 2.0, or aluminium oxidehaving a thickness of 3 nm or more. A even higher degree of reflectionmay be obtained using a plurality of double layers 2·λ/4 alternatingwith low and high refractive indices.

Accordingly, the present invention includes reflectors containing areflector body, if desired a pre-treatment layer which is deposited onthe reflector body or is formed out of this itself, deposited on top ofthat the functional coating, and on top of that the reflection layerstructure. The reflection layer structure itself exhibits the reflectionlayer, which as a rule lies on the functional layer. In one version oneor more transparent layers of optical thickness λ/2, which in turn arecovered by the protective layer, may lie on the reflecting layer.Consequently, the layer described as the protective layer alwaysrepresents that layer on the reflector which lies outermost, is free anddirectly exposed to mechanical influences.

All or individual layers in the refection layer structure b) may e.g. bedeposited onto the reflector body or onto a pre-treatment layer thereone.g. by gas or vapour-phase deposition in vacuum (physical vapourdeposition, PVD), by thermal vaporisation, electron beam vapourdeposition, with and without the assistance of ionisation, bysputtering, in particular magnetron sputtering, by plasma-polymerisationor chemical gas phase deposition (chemical vapour deposition, CVD) withand without the assistance of plasma. Other methods of deposition arelacquering or immersion using solutions manufactured in the sol-gelprocess followed by drying, flame-pyrolitic process or flame coatingusing SiO₂. It is also possible e.g. to suppliment PVD-layers byflame-coating with SiO₂.

The reflecting layer or reflecting layer structure may be deposited onthe surface e.g. in a process structure which includes—possiblydegreasing and cleaning—charging the item with the surface to be coatedinto a vacuum unit, cleaning e.g. by means of sputtering, glowdischargeetc., in a first step deposition of a light-reflecting, in particularmetallic layer, and in a second step deposition of a transparent layerand if desired in a third, fourth etc. step deposition of a second,third etc. transparent layer and discharging the coated item from thevacuum.

The reflecting layer may also be produced in an electrolytic or wetchemical process. The transparent layers and thereby in particular theprotective layer may be present as gel-films which are produced in asol-gel process. The transparent layers and thereby in particular theprotective layer may also be produced in a flame-pyrolitic manner. It isalso possible to employ different processes for the individual layers ina layer structure.

For example in the case of rolled products such as foils, strips orsheets or in the case of laminates with an aluminium layer, individualor advantageously all coatings are deposited or precipitated in acontinuous manner, as a rule using the so called strip or continuousprocesses, also known as coil-coating. For the production of thepre-treatment layer e.g. the method of anodic oxidation of aluminium maybe employed. Also the functional coating a) e.g. a sol-gel layer may bedeposited in a continuous process, whereby the sol is deposited onto thesurface to be coated by immersion, spraying etc. or in coil coating andsubsequently dried or hardened by radiation and/or heat treatment in thecontinuous heat treatment furnace. Finally, the reflection layer b) maybe deposited by vapour deposition, sputtering etc in each case in vacuumetc.

The structure of reflection layers b) on the reflector body serves inparticular the reflection of electromagnetic radiation or energy in theform of waves and/or particles, usefully for the reflection of radiationwith wavelengths in the optical range and preferably visible light, inparticular those waves with wavelengths between 400 and 750 nm.

The reflectors according to the invention with surfaces that bear thereflection layer structure according to the invention exhibit excellentreflecting properties e.g. for electromagnetic radiation and inparticular electromagnetic radiation in the optical range. The opticalrange includes e.g. the infra-red radiation, the visible light range,the ultra-violet light range etc. The preferred field of application isthe range of electromagnetic radiation and thereby the visible lightrange.

The reflection of radiation may, depending on the surface, bedirectional, scattered or a combination thereof. Accordingly, thereflectors according to the invention are suitable as reflectors such asreflectors e.g. for radiation sources or optical equipment. Suchradiation sources are e.g. lamps, such as lamps for workplaces, primarylighting, secondary lighting, strip lighting, light guiding elements,lighted ceilings, light deflecting lamellae or thermal radiators. Thereflectors may e.g. also be mirrors or interior mirrors of opticalequipment, lamps or thermal radiators.

The reflector layer structure b) on the reflecting body leads inparticular to reflectors whose coated surfaces exhibit a totalreflection—measured acc. to DIN 5036—usefully of 90% and more, inparticular from 94 % to 96 % and more.

The reflectors according to the present invention exhibit e.g. excellentresistance to wiping and also hardness. The resistance to wiping can bemeasured e.g. acc. to DIN 58196. In summary according to DIN 58196 asample is tested using a felt type stamp applied with a force of 4.5N(corresponds approx. to 450 g) over a stretch of 120 mm 100 times within74 seconds (1.3 Hz). The test cycle is repeated 20, 50 and 80 times; thesample is then evaluated. On a scale of 1 to 5 the value 1 represents nodamage to the surface, 2 means traces of rubbing can be recognised onviewing under special lighting in a light box, 3 means traces of rubbingcan be recognised on viewing in daylight, 4 means pronounced traces ofrubbing are to be seen over the whole area and 5 means very pronouncedtraces of rubbing are to be seen over the whole surface area. Thereflectors, for example in the form of foils, strips or sheets can beshape formed and namely such that it is hardly possible to detectcracks. The reflectors according to the invention exhibit goodprotection against mechanical effects such as mechanical damage e.g.scratch hardness or wear and thereby in particular a high resistance towiping. Mechanical damage can occur e.g. as a result of cleaning thesurface i.e. the reflecting layers, due to dust, sand and the like whichbecomes trapped between the cleaning device and the surface or due tothe cleaning equipment itself such as dusters, wipers, brushes etc.

The scope of the present invention includes also the use of reflectorscontaining a surface that is resistant to mechanical attack having hightotal reflectivity for reflection of radiation in the optical range i.e.daylight and artificial light, thermal radiation, visible light,ultra-violet light etc. Of particular importance is the use of thereflectors for reflecting visible light, in particular daylight orartificial light, including ultra-violet light. The reflectors accordingto the invention are e.g. suitable as reflectors or lighting elements inlighting or illumination technology such as e.g. reflectors in lamps forworkplaces where display units with screens are in use, primarylighting, secondary lighting, strip lighting, light guiding elements,lighted ceilings or as light deflecting lamellae etc.

EXAMPLES

Various samples for testing made of aluminium or its alloys werepre-treated by anodising, some only degreased, and subsequently coatedwith a lacquer. A reflecting layer structure was deposited onto thelacquer using a PVD process. The reflecting layer structure comprised inseries: a 50 nm thick reflecting aluminium layer onto which wasdeposited first a silicon oxide layer with an optical thickness of λ/4and after that a titanium oxide layer having an optical thickness ofλ/4. In accordance with the invention the protective layer was depositedonto the outermost surface in a further PVD process, this in the form ofa 5 to 10 nm thick SiO₂ layer. In the examples used for comparisonpurposes the protective layer was missing in each case. All samples weresubjected to the wipe test acc. to DIN 58196 and the resistance towiping evaluated. The samples according to the invention were evaluatedafter 50 test cycles each of 100 strokes. The comparison samplesdegenerated so fast during the wipe test that the number of cycles isgiven at which a value of 3 or higher, up to 5, was reached. The testingarrangements and the values achieved are presented in the followingtable. From the following table it can be seen that the protective layerleads to a considerable improvement in the resistance to wiping. Afterinterrupting the test at 50 cycles, each of 100 strokes, all of thesamples according to the invention still exhibit an undamaged surfacewith a value of 1. The samples used for comparison on the other hand hadfallen significantly and already after less than 10 or 20 cycles thesamples were so damaged that the value of 3 or worse had been reached.

TABLE Wipe-test: Reflection layer Protective number of test Sample No.Substrate Pre-treatment Lacquer structure layer cycles = value 1 Al99.7anodised Sol-gel¹⁾ Al/SiO₂/TiO₂ SiO₂ 50x = 1 Comparison 1 Al99.7anodised Sol-gel¹⁾ Al/SiO₂/TiO₂ none Less than 10x 2 Al99.9 degreasedSol-gel¹⁾ Al/SiO₂/TiO₂ SiO₂ 50x = 1 Comparison 2 Al99.9 degreasedSol-gel¹⁾ Al/SiO₂/TiO₂ none Less than 20x 3 AlMgCu degreased SiO₂/TiO₂Al/SiO₂/TiO₂ SiO₂ 50x = 1 Sol-gel mixture Comparison 3 AlMgCu degreasedSiO₂/TiO₂ Al/SiO₂/TiO₂ none Less than 10x Sol-gel mixture 4 AlMgCudegreased Sol-gel on Al/SiO₂/TiO₂ SiO₂ 50x = 1 polysiloxane basisComparison 4 AlMgCu degreased Sol-gel on Al/SiO₂/TiO₂ None Less than 20xpolysiloxane basis 5 Al99.7 Barrier layer Sol-gel¹⁾ Al/SiO₂/TiO₂ SiO₂50x = 1 150 nm Al₂O₃ Comparison 5 Al99.7 Barrier layer Sol-gel¹⁾Al/SiO₂/TiO₂ none Less than 20x 150 nm Al₂O₃ ¹⁾with organic content

What is claimed is:
 1. A reflector with high total reflection, andresistant to mechanical stress, containing a reflector body made of arolled metal sheet on which are superimposed: (a) a functional coatingcomprising a gel film, varnish or polymer with a thickness ranging from0.5 to 20 μm, the functional coating overlying and being directly on thereflector body; and (b) a reflection layer structure composed of (i) areflecting metallic layer overlying and being directly on the functionalcoating; (ii) a plurality of transparent layers overlying the reflectingmetallic layer, one of the transparent layers being directly on thereflecting metallic layer, and each of the other transparent layersoverlying and being directly on one of the transparent layers, and (iii)a scratch proof protective layer overlying and being directly on thetransparent layer furthest away from the reflecting metallic layer,surface of the protective layer away from the reflector body has nolayer thereon, the protective layer comprises a silicon oxide of formulaSiO_(x) where x represents a number from 1.1 to 2.0 or aluminum oxide offormula Al₂O₃, the protective layer has a thickness of 3 nm to 20 nm,the protective layer, being on the surface of the reflector away fromthe reflector body, protects underlying layers against mechanicaldamage, and the protective layer exhibits no surface damage in wipe testaccording to DIN 58196 after 50 test cycles each of 100 wiping strokes.2. The reflector according to claim 1, wherein the protective layer is asilicon oxide having the general formula SiO_(x) where x is a numberfrom 1.1 to 2.0.
 3. The reflector according to claim 1, wherein theprotective layer is a silicon oxide having the general formula SiO_(x)where x is the number 1.8.
 4. The reflector according to claim 1,wherein the protective layer is a gel film deposited in a sol-gelprocess or a thin film deposited in vacuum or a plasma deposited thinfilm or a film created in a flame-pyrolitic manner.
 5. The reflectoraccording to claim 1, wherein the reflection layer structure comprises ametallic reflecting layer with 1, 2, 3, 4, 5, 6, 7, 5, 9 or 10transparent layers of optical thickness λ/2±40 nm arranged thereon,where the transparent layers are double layers in each case two layersof thickness λ/4, and deposited thereon the protective layer.
 6. Thereflector according to claim 5, wherein the double layers, each of twolayers, are of thickness equal to λ/4 and comprise a low refractiveindex layer of thickness λ/4 and a high refractive index layer ofthickness λ/4.
 7. The reflector according to claim 6, wherein the doublelayers, each of two layers, are of thickness equal to λ/4 and comprisinga low refractive index layer of thickness λ/4 or of SiO₂ or MgF₂ and ahigh refractive index layer of thickness λ/4, or of titanium oxide,Ti,Pr-oxide or tantalum oxide.
 8. A process comprising preparing thereflector according to claim 1 as a reflector or a light-guiding elementfor artificial light and daylight.
 9. A combination of a reflectoraccording to claim 1, in a lamp for a workplace where a display unitwith a screen is in use, primary lighting, secondary lighting, striplighting, lighted ceiling or as light deflecting lamella.
 10. Areflector with high total reflection, and resistant to mechanicalstress, containing a reflector body made of a rolled aluminum sheet onwhich are superimposed: (a) a functional coating overlying the reflectorbody, the functional coating being anodically oxidized aluminum formeddirectly out of the aluminum lying on surface of the reflector body, ofthickness 10 to 500 nm, and a gel-film, lacquer or polymer of thickness0.5 to 20 μm overlying and being directly on the anodically oxidizedaluminum; and (b) a reflection layer structure composed of (i) areflecting metallic layer overlying and being directly on the functionalcoating, (ii) a plurality of transparent layers overlying the reflectingmetallic layer, one of the transparent layers being directly on thereflecting metallic layer, and each of the other transparent layersoverlying and being on one of the transparent layers, and (iii) ascratch-proof protective layer overlying and being directly on thetransparent layer furthest away from the reflecting metallic layer, andsurface of the protective layer away from the reflecting body has nolayer thereon, the protective layer comprises a silicon oxidesilicon-oxide of formula SiO_(x) where x represents a number from 1.1 to2.0, or aluminum oxide of formula Al₂O₃, the protective layer has athickness of 3 nm to 20 nm, the body, protect underlying layers againstmechanical damage, and the protective layer exhibits no surface damagein wipe test according to DIN 58196 after 50 test cycles, each of 100wiping strokes.
 11. The reflector according to claim 10, wherein theprotective layer is a silicon oxide having the general formula SiO_(x)where x is a number from 1.1 to 2.0.
 12. The reflector according toclaim 10, wherein the protective layer is a silicon oxide having thegeneral formula SiO_(x) where x is the number 1.8.
 13. The reflectoraccording to claim 10, wherein the protective layer is a gel filmdeposited in a sol-gel process or a thin film deposited in vacuum or aplasma deposited thin film or a film created in a flame-pyroliticmanner.
 14. The reflector according to claim 10, wherein the reflectionlayer structure comprises a metallic reflecting layer with 1, 2, 3, 4,5, 6, 7, 5, 9 or 10 transparent layers of optical thickness λ/4±40 nmarranged thereon, where the transparent layers are double layers in eachcase two layers of thickness λ/4, and deposited thereon the |protectivelayer.
 15. The reflector according to claim 14, wherein the wavelengthof the reflected electromagnetic radiation lies in the range of visiblelight.
 16. The reflector according to claim 14, wherein the wavelengthof the reflected electromagnetic radiation lies between 400 and 750 nm.17. The reflector according to claim 14, wherein the double layers, eachof two layers, are of thickness equal to λ/4 and comprise a lowrefractive index layer of thickness λ/4 and a high refractive indexlayer of thickness λ/4.
 18. The reflector according to claim 17, whereinthe double layers, each of two layers, are of thickness equal to λ/4 andcomprising a low refractive index layer of thickness λ/4 or of SiO₂ orMgF₂ and a high refractive index layer of thickness λ/4, or of titaniumoxide, Ti,Pr-oxide or tantalum oxide.
 19. A process comprising preparingthe reflector according to claim 10, as a reflector or a light-guidingelement for artificial light and daylight.
 20. A combination of areflector according to claim 10, in a lamp for a workplace where adisplay unit with a screen is in use, primary lighting, secondarylighting, strip lighting, lighted ceiling or as light deflectinglamella.
 21. The reflector according to claim 1, wherein the reflectorbody is composed of a rolled aluminum or aluminum alloy sheet.
 22. Thereflector according to claim 1, wherein the reflector structure (b) onthe reflecting body provides the reflector whose coated surface exhibitsa total reflection, measured according to DIN 5036, of 90 percent andmore.
 23. The reflector according to claim 22, wherein the coatedsurface of the reflector exhibits a total reflection, measured accordingto DIN 5036, of 94 to 96 percent.
 24. The reflector according to claim23, wherein the coated surface of the reflector exhibits a totalreflection, measured according to DIN 5036, of 96 percent or more. 25.The reflector according to claim 10, wherein the reflector structure (b)on the reflecting body provides the reflector whose coated surfaceexhibits a total reflection, measured according to DIN 5036, of 90percent and more.
 26. The reflector according to claim 25, wherein thecoated surface of the reflector exhibits a total reflection, measuredaccording to DIN 5036, of 94 to 96 percent.
 27. The reflector accordingto claim 26, wherein the coated surface of the reflector exhibits atotal reflection, measured according to DIN 5036, of 96 percent or more.